JPH08212910A - Formation method of hole into photosensitive resin layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disclose a method for forming holes into a photosensitive resin layer employed in the manufacture of an electron source having a microchip in a emissive cathodes and of a flat display screen. SOLUTION: A resin layer 22 is exposed to exposure light 26 through transparent singlelayer balls 28, the light is focused on the resin layer by each ball, the region of the resin layer is thereby exposed, and the resin layer thus exposed is developed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming holes in a photosensitive resin layer.

The invention more particularly corresponds to the production of electron sources having microtips in the emitting cathode and can be used in particular for producing display means by field emission excited cathodoluminescence.

The invention makes it possible in particular to produce large microtip flat screens, for example larger than 14 inches (approximately 35 cm) and having a surface area close to 1 m ² .

The invention is further applicable to the manufacture of etched antireflection layers for microchips, sensors and antireflection layers for radar waves.

[0005]

Electron sources whose emission cathodes have microtips and methods for their production are described, for example, in the following references: (1) FR-A-2593953 (EP-A-2349).
89 and US-A-4857161), (2) FR-A-2687839 (EP-A-5583).
See also 93).

In order to facilitate understanding of the technical problems solved by the present invention, a well-known example of a method of manufacturing an electron source having a radiation cathode and a microchip will be described below with reference to FIGS. 1 to 3. Enter.

FIG. 1 shows a cathode conductor 6 on a substrate 2 on which an insulator 4 is mounted, a grid 8 superimposed on the intermediate insulator 10 in a crossed manner, and the role of a mask during the manufacturing process of the microchip. And a layer 12 deposited on the surface for the purpose of making, for example, nickel 12 and showing a structure already produced.

The nickel layer 12, the grid 8 and the insulator 10 have holes 14 formed above the buttons of the holes by a conductive metal electrically connected to the cathode conductor. The formed microchips are deposited one after another.

Next, manufacturing of the microchip will be described with reference to FIG. First, the deposition yields a molybdenum layer 16, for example, over the structure. The layer 16 has a thickness of approximately 1.
It is 6 μm. The layer 16 is deposited perpendicular to the surface of the structure.

Due to the progress of this deposition, hole 1
A molybdenum cone 18 located within 4 and having a height of 1.4 μm to 1.5 μm is obtained. These cones constitute the electron emitting microchip 18.

After this, as shown in FIG. 3, an electrochemical method is used to remove the nickel layer 12 in order to expose the electron-emissive microtips 18, for example made of niobium, and to free the perforated grid 8. Selective dissolution is performed.

Apart from some technical variants, the method described in FIGS. 1, 2 and 3 has been used up to now for producing a microtip of an electron source having a microtip in the emitting cathode. Is.

In order to properly size and position the microchip 18, it is clearly necessary to accurately control the size of the holes made in the grid 8 and in the insulator 10.

Therefore, the following problems occur. It is a problem to fabricate on all surfaces to receive microtip holes with an average diameter of eg 1.3 μm or less.

The method currently used to do this is photolithography using direct spraying, or repeating photographs of the basic pattern reproduced on all surfaces. For large electron sources over 14 inches (nearly 35 cm), these methods are subject to large constraint characteristics very quickly.

Direct spraying requires the production of large, l-sized masks with submicron patterns. It is difficult to manufacture the mask with a diagonal of more than 14 inches.

A small mask is used in the photo-repetition, said size being determined by the resolution of the pattern used. Since a mask having a size of 20 mm to 50 mm is used on the side surface for a resolution of 1 μm, it is necessary to repeat the exposure operation a very large number of times, and it is necessary to perform photolithography to cover the entire surface of the electron source. .

These two methods (one being a direct spraying method and the other being a photo-repeat method) are therefore difficult to use for producing large electron sources.

[0019]

The present invention makes it much easier to produce holes than the known methods described above.

The present invention relates to a very simple method of forming holes in a photosensitive resin layer. The present invention allows the formation of holes that are approximately 1 μm or less on large or small diameter surfaces.

According to the present invention, the photosensitive resin layer can be exposed at points corresponding to the positions of the holes formed in the resin.

[0022]

When the resin is developed (ie, after the exposed areas have been melted), the resin serves to form holes as a mask in the structure in which the resin is located. Considering, for example, the structure described in connection with FIGS. 1-3, the resin layer serves to etch the grid 8 and the intermediate insulator 10 after being developed.

More particularly, the present invention relates to a method of forming holes in a positive photosensitive resin layer by exposure light, said method comprising the following steps: -Transparent to said exposure light. And forming a single-layer ball that is in direct contact with the resin layer; -The resin layer is exposed by the exposure light through the single-layer ball, and each ball makes a contact point between the ball and the resin layer thereabove. , The light is concentrated to expose the region of the resin layer, and the exposed light forms a beam collimated in parallel with a constant light intensity over the entire monolayer of the ball. The exposed resin layer is developed and holes are formed in the exposed layer.

The first advantage of the method according to the invention is that it is very simple compared to the conventional photolithography method. No special mask is used in the method of the present invention and no precise alignment step is required.

A second advantage of the present invention is that it allows the handling of large surfaces and the production of large electron sources with microtips.

Thus, in order to handle the surface according to the present invention, it is necessary to spread it over a photosensitive resin, and the dimensions of the surface are not a problem after the resin has been dried in order to cover the surface with balls.

Other advantages of the present invention will be apparent from the following.

Balls with a diameter of, for example, 1 μm to 10 μm can be used to implement the invention.

The invention also relates to a method for producing an electron source in which the emitting cathode has a microtip on the basis of the following: the structure is a cathode conductor on a substrate and an electrical conductor on said cathode conductor. Electrically insulated layer, and further on said electrically insulated layer a grid angling with the cathode conductor, and-in the region where the grid intersects the cathode conductor, The holes are formed through the grid and the insulating layer, -microtips of the electron emitting material are formed in the holes above the cathode conductor. According to the above method, holes form a positive photosensitive resin layer on the surface of the structure, holes are formed in the resin layer based on the hole forming method of the present invention, and the holes formed in the resin layer are passed through the grid. And is obtained by etching the insulating layer.

Thus, the resin layer is used as a mask to form the holes used to insert the microchips in the substructure.

There is an advantage that a region where no hole is formed can be kept separate by the partition mask opaque to the exposure light. This partition is placed between the exposure light source and the single layer ball.

[0032]

FIG. 4 shows schematically and partly the structure associated with the description of FIGS. 1 to 3, the substrate 2,
Insulator 4, cathode conductor 6, grid 8 and intermediate insulator 1
It has 0.

Producing holes in the grid 8 and the intermediate insulator 10 is carried out by the method according to the invention.

A positive photosensitive resin layer 22 is deposited on the side surface of the structure 20 of FIG. 4 to form a side hole. On top of the resin layer is deposited a monolayer 24 of balls that are transparent to the light 26 used to expose the resin layer.

This resin passes through the ball layer 24 and the resin layer 2
It is exposed by light 26 that is perpendicular to 2. This light 26 forms a collimated collimated light beam having a constant light intensity over the entire surface of the monolayer ball, said beam coming from a light source not shown.

As can be seen in FIG. 5, each of the balls 28 concentrates the light at the contact point between the ball and the resin layer 22, and in the region 30 of the resin layer at the contact point between the ball and the resin layer. Exposed.

Next, it is necessary to remove the balls from the surface of the structure 20 and develop the exposed resin layer (in other words, the exposed resin region is melted), and at the position of the exposed region 30. Holes 31 are formed in the resin layer.

Further, the ball can be taken out by leaving the ball on the resin layer, developing the exposed resin layer, and passing a solvent used for dissolving the exposed region through a filter.

In order that the entire thickness of the resin is exposed in the region 30, said thickness should be reduced to the same order of magnitude as the spot of the light, for example 1 μm.

An expert selects the size and refractive index for the ball and adds a spot of light of appropriate diameter.

For example, silica balls are used for exposure light close to ultraviolet rays.

Clearly, a resin is used that ensures that the attack rate, which is a function of the exposure light it receives, is not affected by parasitic exposure light passing between the balls.

Considering FIG. 5, an advantage is added to the method according to the invention: the diameter D of the spot light produced by each ball is approximately 1 μm or less by choosing an appropriate diameter D1 and exposure time for the ball. The value of can be easily adjusted.

The balls transparent to the exposure light concentrate the light beams at the contact points between the glass balls and the photosensitive resin layer. The surface of the generated spot light is not uniformly irradiated. The intensity of light is maximum in the center of the spot and slows towards the edges. By operating only the exposure time, it is possible to adjust the diameter of the exposed region and the diameter of the hole over the entire thickness of the photosensitive resin layer.

The less the resin layer is exposed through the ball, the smaller the surface of the resin layer that is exposed and therefore soluble, and also the size of the holes formed in the resin and hence the grid. And the size of the holes formed through the holes in the intermediate insulator becomes smaller.

Since the size of the holes formed in the grid and the intermediate insulator is small, the control voltage of the microchip can be conveniently lowered.

In the case of FIGS. 4 and 5, the balls deposited on the surface of the structure 20 are in contact with each other.

In this case, an additional advantage of the method according to the invention is that the diameter D1 of the balls 28 is formed in the resin layer and the spacing E between the centers is fixed. Therefore, for example, a calibration ball is selected and its diameter is 1 μm.
To 10 μm. Further, the microball will be described.

FIG. 6 schematically shows that non-contact, randomly distributed monolayer balls can be deposited on the surface of the resin layer 22.

To obtain a non-contact monolayer of balls, it is possible to use, for example, the method of depositing said balls on the surface of the photosensitive layer: spraying the balls in a water-ethanol mixture solution. The ability to use non-contact balls provides another advantage of the present invention in that the amount of exposure is around the non-contact balls, such as area 32 in FIG.
This is because there are more concentrated points (exposed areas 30) than inside.

Next, using the method according to the invention, the holes 14 are associated with the grid 8 and the intermediate insulator 1 in connection with FIGS.
How it is formed in 0 will be described.

More specifically, it is desired to form a microtip emitting cathode source, so that the first step is to provide the aforementioned insulator 4, cathode conductor 6, and intermediate insulator on the substrate 2. 10 to form the grid 8.

If it is necessary to show that this is necessary, masking is done in one or more areas where holes are not produced. To do this, reference (2) above.
Please refer to.

Next, according to the present invention, the photosensitive resin layer 22
Are spread over the entire surface of the resulting structure 20. The resin layer 22 has a thickness of 1.2 μm and a refractive index of 1.
7 The resin layer is then warmed and hardened.

The monolayer of glass balls 24 is then either centrifuged or sprayed and spread over the surface of the resin layer 22. The ball has, for example, a diameter of 4 μm and a refractive index of 1.5.

The resin is then exposed through the single layer ball with light of a wavelength of 500 nm. The balls are then removed from the resin layer thus exposed and the resin is developed, ie the resin is dissolved in the exposed areas. In this way holes are obtained at the locations of the exposed areas.

In order to remove the balls from the resin layer, it is necessary to use a liquid that moves the balls poured onto the resin layer.

Ultrasound is used to promote ball separation.

Deionized water is used, for example, as a liquid to be carried or moved, which liquid is filtered and the balls retrieved.

It is not possible to remove the balls from the resin layer before developing. The balls are then removed while the resin dissolves in the exposed areas and the solvent used for development is recovered by filtering.

After the holes are thus obtained in the resin layer, the following is performed in the method of manufacturing the electron source in which the emission cathode has the microchip.

The grid 8 and the intermediate insulator 10 are formed through the holes formed by etching the resin layer, and the holes 14 are formed therein (FIG. 1). The resin layer is then removed.

Under the close proximity, a nickel layer 12 is deposited on the resulting structure. The molybdenum layer 16 is then deposited, the microchip 18 is formed, and the nickel layer 12 and the molybdenum layer 16 are removed.

Another method according to the invention is shown in FIG. According to this other method, the balls are not directly deposited on the surface of the photosensitive resin layer 22. These balls 28 are held on a flat support 33 which is transparent to the exposing light.

In this way, a single layer ball added to the photosensitive resin layer 22 is obtained. The photosensitive resin layer 22 is then irradiated through the transparent support 33 and the balls 28.

To hold the balls 28 on the support 33, a binder 34 made of a polymer such as polyethylmethacrylic acid or a gel such as colloidal silica is used.

Since the balls are kept on the support 33 by the binder 34, for example, a mixture of the balls and the binder can be centrifuged on the surface of the support 33.

As an alternative to keeping the balls on the support 33, the balls are mixed with a liquid such as a mixture of deionized and ethanol or a liquid such as pure ethanol.

The liquid layer is spread on the support 33 and the dehydrated liquid. As a result, the single-layer ball is the support 3
Obtained over 3. In this case, the ball is held on the support 33 by the force of static electricity.

For example, a silica support 33 is used for exposure light close to ultraviolet rays.

[Brief description of drawings]

FIG. 1 is a schematic and partial view of a known method of manufacturing an electron source having a microtip on the emitting cathode.

FIG. 2 is a schematic and partial view of a known method of manufacturing an electron source having a microtip on the emitting cathode.

FIG. 3 is a schematic and partial view of a known method of manufacturing an electron source having a microtip on the emitting cathode.

FIG. 4 is a schematic partial view of a contacted single layer ball implementing a method according to the present invention.

FIG. 5 is a schematic diagram of a method according to the present invention.

FIG. 6 is a schematic view of another method according to the present invention using a single layer non-contact ball.

FIG. 7 is a schematic view of another method according to the present invention using a single layer ball formed on a support.

[Explanation of symbols]

 2 Substrate 4 Insulator 6 Cathode Conductor 8 Grid 10 Intermediate Insulator 12 Nickel Layer 14 Hole 16 Molybdenum Layer 18 Electron Emission Microchip 20 Structure 22 Resin Layer 24 Ball Single Layer 26 Exposed Light 28 Ball 30 Exposed Area 32 Area 34 binder

Claims (15)

[Claims] 1. Forming a single layer (24) of balls (28) transparent to exposure light (26) and in direct contact with the resin layer, the resin layer being exposed by the exposure light through the single layer ball. The light is concentrated by each ball at the contact point between the ball and the resin layer on the ball, and the region of the resin layer (30)
Exposure is performed and the exposed light forms a collimated beam with constant light intensity across the monolayer ball, thus exposing the exposed resin layer located in the exposed area. A method of forming a hole in the positive photosensitive resin layer (22) by the exposure light (26), comprising the steps of forming a hole in the layer. 2. Method according to claim 1, characterized in that the balls (28) are in contact with each other. 3. The method according to claim 1, characterized in that the balls (28) are not in contact with each other. 4. The method according to claim 3, wherein the non-contact balls are randomly distributed. 5. Method according to claim 1, characterized in that a monolayer (24) of balls is formed by deposition on the surface of the photosensitive resin layer (22). 6. The ball (28) is a photosensitive resin layer (22).
Method according to claim 5, characterized in that it is deposited by centrifugation on the surface of the. 7. The ball (28) is a photosensitive resin layer (22).
A method according to claim 5, characterized in that it is deposited by spraying on the surface of the. 8. The ball (28) is a photosensitive resin layer (22).
6. The method according to claim 5, characterized in that after being developed, it is removed from the surface of the photosensitive resin layer. 9. The photosensitive resin layer (2) is provided by entraining a ball (28) by a liquid or in a bath subjected to ultrasonic action.
Method according to claim 8, characterized in that it is removed from 2). 10. Method according to claim 5, characterized in that the ball (28) is placed on the resin layer until it has been developed and is entrained in a bath for the development of said layer. 11. A single layer (24) of the ball is exposed to light (2).
Method according to claim 1, characterized in that the balls are held on a transparent support (33) in 6) and the balls thus held are added to the surface of the photosensitive resin layer (22). . 12. Method according to claim 11, characterized in that the ball (28) is held on the support (33) by the force of a binder or electrostatics. 13. Method according to claim 1, characterized in that the diameter of the balls (28) is approximately 1 μm to 10 μm. 14. A structure (20) comprising a cathode conductor (6) on a substrate (2), an electrically insulated layer (10) on said cathode conductor, and further said electrically isolated. A layer (8) that is angled to the cathode conductor on the layer formed by the formation of holes, and in the region where the grid intersects the cathode conductor, holes (14) are formed through the grid and the insulating layer. Based on that a microtip (18) of electron emitting material is formed in a hole above the cathode conductor,
Further, holes (14) form a positive photosensitive resin layer (22) on the surface of the structure (20), and holes are formed in the resin layer (22) based on the hole forming method according to the present invention. A method of manufacturing an electron source having a microtip as a radiation cathode, which is obtained by etching a grid and an insulating layer through the holes formed in the. 15. A flat screen using an electron source obtained by the method according to claim 14.